Reductive heat exchange water and heat exchange system using such water

ABSTRACT

Heat exchange water for cooling an object of heat exchange such as machinery, air, or liquid, which serves to prevent oxidation and deterioration of metal materials used in pipes for supplying/circulating the heat exchange water or in the liquid ends of the heat exchanger, to suppress growth of algae and microorganisms, and to reduce influence on the environment. The heat exchange water is reductive water having zero or negative standard oxidation-reduction potential as determined on the basis of the hydrogen electrode standard.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to heat exchange water and a heatexchange system for performing heat exchange with respect to an objectof heat exchange such as machinery, air, or liquid.

[0003] 2. Description of the Background Art

[0004] Heat exchangers for cooling objects of heat exchange such asmachinery, air, or liquid are widely used in factories and laboratoriesin many fields. Conventionally, in these heat exchangers, water such ascity water and industrial water are employed as the heat medium forperforming heat exchange because water is safe to handle, inexpensive,and suitable as a heat medium due to its high specific heat and highheat transfer rate.

[0005] Conventional systems for supplying the heat medium, namely, theheat exchange water, are configured as shown for example in FIG. 11.Specifically, the heat exchange water is forwarded by a circulating pump51 to a cooler 52 that cools the heat exchange water using water 521.The heat exchange water is cooled in this cooler. The heat exchangewater is sometimes hereinafter referred to as the cooling water.Subsequently, the cooled heat exchange water (cooling water) isforwarded to a cooling device 57, and is used for cooling an object ofheat exchange 571 passing through the cooling device 57. The heatexchange water after being used for cooling is transferred back to theinlet side of the circulating pump 51 through piping 54 connectingthereto and forming a circulation system. When the quality of the heatexchange water degrades within this circulation system, the water ispartially or completely discharged through a discharge pipe 56. Make-upwater is then supplied to the circulation system after being treated inthe pre-treatment device 59.

[0006] Heat exchangers using conventional water as the heat medium havethe following shortcomings.

[0007] (1 ) Water used as the heat exchange water contains dissolvedoxygen or oxidizers such as hypochlorous acid and sodium hypochloritedissolved therein for sterilization. By the oxidizing effects of thesecomponents, metal materials used in the water supply piping system andthe liquid ends of the heat exchanger become oxidized. As a result, (i)oxide films or, when aggravated, tumorous protrusions are formed in theliquid ends. This greatly decreases the heat exchange efficiency, andincreases resistance in the piping system (heat exchange system) toimpede flow of a specified quantity of heat exchange water. In addition,(ii) the thickness of metal liquid ends is decreased by oxidation anddissolution. The mechanical strength of these components is therebylost, possibly causing a fracture in the components which leads toleakage of the heat exchange water. Furthermore, (iii) problems in theheat exchange system such as filter clogging occur because of thegeneration of so-called “rusty water” and the increase in turbiditycaused by metal fragments that have flaked off due to corrosion.

[0008] (2 ) To solve the above problems, facilities are often providedfor adding chemicals such as rust-preventatives. These chemicals musttherefore be constantly purchased and stocked, resulting in costs forboth the purchase and the storage space. During blowdown of the heatexchange water bearing rust preventives, measures must be taken tominimize impacts on the environment caused by the discharge of suchwater.

[0009] (3 ) The concentration of dissolved oxygen can be reduced bydeaerating the heat exchange water in order to prevent oxidation bydissolved oxygen. However, oxidation and corrosion of the metalmaterials cannot sufficiently be avoided by simply reducing oxygendissolution.

[0010] (4 ) There are cases where algae and microorganisms proliferatein the heat exchange system, forming biological films on the liquidends. This may cause decrease in the heat exchange efficiency andincrease in resistance inside the pipes. Chemicals such as germicidesmust then be added, entailing increased costs and environmental problemsas in the above (2 ).

[0011] (5 ) The flow rate of the heat exchange water circulating in theheat exchanger is usually set at a rate including margins such that theobject of heat exchange can be cooled to below a predeterminedtemperature even when the object generates the maximum heat load. Theflow rate is not separately controlled for discrete objects. Despite thefact that the heat radiation load amount of the objects varies widelydepending on operating conditions, and that no heat is generated whenthe operation of the facility is stopped, it is typical in conventionalsystems that the heat exchange water is constantly circulated at a flowrate fixed according to the maximum heat radiation load. In other words,depending on the situation of operation, most of the heat exchange watermay be circulating wastefully. Further, while the supplying temperatureof the heat exchange water is usually room temperature, the exitingtemperature is approximately 5° C. higher than the supplyingtemperature. As it is necessary to minimize the difference between thesupplying and the exiting temperatures of the heat exchange water, ahigh flow rate of heat exchange water is presently used in conventionalsystems. For these reasons, in factories having many installationsrequiring heat exchange, a heat exchange system for circulating heatexchange water at an extremely high flow rate must be provided. In orderto circulate heat exchange water at a high flow rate, the circulationline for the heat exchange water must be made wide to reduce the fluidresistance of the piping, but with certain limits. To complement this,the compressing pressure of the compressing pump is typically increased.However, power consumption of the compressing pump increases inproportion to the pump discharge rate and the number of installed pumps.Accordingly, there exist problems such as high costs and largeinstallation space required by large-capacity pumps and pipes havinglarge diameters, and vibrations caused by large pumps. Moreover, theinfluence on the environment during blowdown of a large quantity of heatexchange water certainly cannot be neglected. As described above, heatexchange water and a supplying system for the water that areenvironmentally benign and can maintain a stable cooling effect at highefficiency for a long period of time were not conventionally available.

SUMMARY OF THE INVENTION

[0012] The purpose of the present invention is to provide heat exchangewater that prevents oxidation and deterioration of metal materials usedin pipes for supplying/circulating the heat exchange water or in theliquid ends of the heat exchanger. The heat exchange water should alsosuppresses growth of algae and microorganisms, and eliminate detrimentaleffects on the environment. Another purpose of the present invention isto provide a simple heat exchange system that can retrofit in existingsystems and that minimizes cost increase. A further purpose of thepresent invention is to perform control for optimal temperature throughadjustment of the flow rate of the heat exchange water to accomplishlower flow rate and lower pressure of the heat exchange water, so as toreduce installation space and vibration due to the pump and to achieve aheat exchange system that minimizes cost increase.

[0013] According to the present invention, in a heat exchanger forcooling an object of heat exchange such as machinery, air, or liquid, areductive water having zero or negative standard oxidation-reductionpotential determined by use of the hydrogen electrode standard, is usedas the heat exchange water for performing heat exchange with the objectof heat exchange.

[0014] According to the above, oxidation and deterioration of metalmaterials used in pipes for supplying/circulating the heat exchangewater or in the liquid ends of the heat exchanger can be prevented.Growth of algae and microorganisms can be suppressed, and impacts on theenvironment can be reduced. Further, as the reductive water can beobtained by, for example, adding hydrogen gas to water, a simple heatexchange system is provided that can retrofit existing systems and thatminimizes cost increase. It is to be noted that not only hydrogen gasbut also but also other reducing agents may be employed.

[0015] In addition, by controlling the flow rate of the heat exchangewater (cooling water) circulating in the heat exchanger (cooling device)for cooling the object of heat exchange, the temperature of the coolingwater can be controlled at a desired temperature. In this way, thecooling water circulating in the cooling device can be best tailored forthe intended purpose, allowing efficient heat exchange with the objectof heat exchange. Such an arrangement contributes to cost reduction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 illustrates a heat exchange system according to a firstembodiment of the present invention.

[0017]FIG. 2 shows a heat exchange system according to a secondembodiment of the present invention.

[0018]FIG. 3 shows a heat exchange system according to a thirdembodiment of the present invention.

[0019]FIG. 4 is a graph illustrating the relationship between thedissolved hydrogen concentration and the standard oxidation-reductionpotential.

[0020]FIG. 5 shows a heat exchange system according to a fourthembodiment of the present invention.

[0021]FIG. 6 shows a heat exchange system according to a fifthembodiment of the present invention.

[0022]FIG. 7 shows a heat exchange system according to a sixthembodiment of the present invention.

[0023]FIG. 8 shows a heat exchange system according to a seventhembodiment of the present invention.

[0024]FIG. 9 shows a heat exchange system according to a eighthembodiment of the present invention.

[0025]FIG. 10 shows a heat exchange system according to a ninthembodiment of the present invention.

[0026]FIG. 11 illustrates a conventional heat exchange system.

DESCRIPTION OF PREFERRED EMBODIMENT

[0027] In the present invention, the heat exchanger for performing heatexchange between an object of heat exchange (such as machinery, air, orliquid) and the heat exchange water or cooling water may be a coolingdevice for cooling or a heating device for heating the object of heatexchange in various factories and laboratories. Preferably, the heatexchanger according to the present invention should better be a coolingdevice for cooling apparatus for manufacturing electronic componentssuch as semiconductors and liquid crystal displays.

[0028] The heat exchange water of the present invention is only limitedby the feature that it is a reductive water having zero or negativestandard oxidation-reduction potential determined by use of the hydrogenelectrode standard. The heat exchange water may be, without limitation,water having hydrogen dissolved therein, or water including a smallamount of dissolved reducing agent other than hydrogen gas such assodium sulfite and sodium hydrogensulfite. Hydrogen-dissolved water ispreferable because the standard oxidation-reduction potential can beeasily controlled by dissolving a small amount of hydrogen in the water,and because hydrogen gas has less impacts on the environment compared toother reducing agents. The water for dissolving the reducing agent maybe any of tap water, river water, industrial water, filtered waterobtained by eliminating particles and oxidizers such as hypochlorousacid and sodium hypochlorite from those waters, and deionized waterobtained by treating those waters in water purifying apparatus toeliminate ionic and non-ionic substances. It is preferable to usedeionized water to prevent system contamination especially when thewater is employed as the heat exchange water in apparatus formanufacturing electronic components. Further, deaerated water ispreferably used as the water for dissolving the reducing agent. Anyknown method can be used to perform deaeration. The preferable level ofstandard oxidation-reduction potential of the reductive water is −0.3Vor lower when determined by use of the hydrogen electrode standard. Thereductive water can be easily controlled to a desired standardoxidation-reduction potential by dissolving an appropriate amount ofhydrogen in water, regardless of the dissolved oxygen concentration inthe reductive water.

[0029] Hydrogen-dissolved water can be obtained by dissolving into waterhydrogen gas that is stored in a gas cylinder or generated byelectrolysis of water. Specifically, hydrogen gas is dissolved intowater such that the dissolved hydrogen concentration in water at 25° C.under 1 atm is 0.1 mg/l or higher, preferably 0.2-1.5 mg/l. Thedissolved oxygen concentration of the water for dissolving hydrogen ispreferably lowered in advance to 3 mg/l or lower, and more preferably to0.1 mg/l or lower, using a known degassing device. The method formeasuring the concentrations of dissolved hydrogen and dissolved oxygenin the water is not restricted to any particular method. For example,the concentrations of dissolved hydrogen and dissolved oxygen indeionized water is preferably measured using diaphragm electrodes. FIG.4 illustrates the relationship between the dissolved hydrogenconcentration and the standard oxidation-reduction potential using thedissolved oxygen concentration as a parameter. As can be seen, in a casewhere the dissolved oxygen concentration is 3 mg/l, the standardoxidation-reduction potential of the water may not be reliablymaintained at a negative value when the dissolved hydrogen concentrationis lower than approximately 0.2 mg/l.

[0030] The following methods can be used, without limitation, todissolve hydrogen gas into water: the method of injecting hydrogen gasinto water via a gas-permeable film; the method of bubbling hydrogen gasdirectly into the piping; the method of using a diffusing device such asa static mixer after injecting hydrogen gas; the method of introducinghydrogen gas from outside, such as introducing hydrogen gas into theupstream side of a pump that supplies ultrapure water into a gasdissolution tank, and allowing hydrogen gas to dissolve by the mixingeffect within the pump; and the method of electrolyzing ultrapure waterand obtaining from the cathode side the reductive water having hydrogengas dissolved therein.

[0031] Referring to FIG. 1, a heat exchange system according to a firstembodiment of the present invention will now be explained. FIG. 1 is adiagram showing an example of the embodiment. The heat exchange system10 a comprises a circulation pump 1, a reductive water cooler 2, adeaerator 9, a reductive water preparing device 3, and a cooling device7 for cooling an object of heat exchange 71. These components areconnected by piping 4 and constitute a substantially sealed circulationsystem. “Substantially sealed” refers to a state which allows leakage ata level that does not obstruct the efficient operation of the presentsupply system. Supply piping 81 for supplying, from the outside of thecirculation system, make-up water treated in a pre-treatment device 61is connected to the inlet side of the circulation pump 1. Dischargepiping 82 for partially or completely discharging circulating water inthe circulation system to the outside of the system is connectedupstream of the supply piping 81. A heat insulating material 73 isdisposed surrounding the piping 4. The heat insulating material 73prevents increase of the circulating water (cooling water) temperaturedue to the influence of the ambient temperature, allowing more efficientoperation.

[0032] The pre-treatment device 61 treats the make-up water beforesupplying it to the circulation system. The treatment method depends onthe type of make-up water, but may be performed by, without limitation,a unit process such as activated carbon adsorption, coagulation,membrane separation, ion exchange, and deaeration, or a device combiningthese process units. Through the pre-treatment device 61, the make-upwater such as filtered water or deionized water can be obtained. Thereductive water cooler 2 may be of any type that can cool thetemperature of the heat exchange water from 30-40° C. to approximately10° C. at the cooler exit. The cooler 2 may comprise, withoutlimitation, a piece of machinery such as a heat exchanger, a coolingtower, and a chiller, or a device performing the cooling by combiningsuch pieces of machinery. Using the reductive water cooler 2, the heatexchange water at the temperature of approximately 10° C. can beobtained. The coolant of the reductive water cooler 2 may be water orair, for example. The object of heat exchange 71 to be cooled in thecooling device 7 may be for example a heat-radiating portion of asemiconductor manufacturing apparatus.

[0033] The reductive water preparing device 3 is composed of a hydrogengas dissolution tank 32 and a hydrogen gas generator 31. Anoxidation-reduction potentiometer 5 and a dissolved hydrogenconcentration meter 6 are connected do the piping between the reductivewater preparing device 3 and the cooling device 7. These measuringdevices are used to constantly monitor the oxidation-reduction potentialand the dissolved hydrogen concentration of the reductive water, and toaccordingly control the amount of hydrogen gas to be dissolved intowater in the hydrogen gas dissolution tank 32. It is not shown in thefigure but a controller is usually included in the above-describedarrangement. The measured values of the oxidation-reductionpotentiometer 5 and the dissolved hydrogen concentration meter 6 aretransmitted to the controller. The amount of hydrogen gas to be suppliedfrom the hydrogen gas generator 31 to the hydrogen gas dissolution tank32 is then controlled according to the measured values transmitted tothe controller. The oxidation-reduction potential (and/or the dissolvedhydrogen concentration) of the reductive water exiting from the hydrogengas dissolution tank 32 is thereby maintained at a predetermined level.The installation locations of the oxidation-reduction potentiometer 5and the dissolved hydrogen concentration meter 6 are not limited to theabove-described locations, and may be downstream of the heatexchanger(cooler 2 ). However, the installation locations are preferablyupstream of the cooling device 7, as in the present embodiment. It isalso possible to provide only one of the oxidation-reductionpotentiometer 5 and the dissolved hydrogen concentration meter 6, and tocontrol the amount of dissolving hydrogen gas according to the obtainedmeasurement values.

[0034] Prior to starting of the operation of this heat exchange system10 a, the internal portions of the circulation system connected by thepiping 4 are preferably sterilized by a bactericide. A known method suchas the method of circulating within the system water containingavailable chlorine dissolved therein can be adopted as the sterilizingmethod.

[0035] Subsequently, while the disinfecting water is discharged via thedischarge piping 82 to the outside of the system, the water treated inthe pre-treatment device 61 is supplied via the supply piping 81 to thecirculation system from the outside of the system, thereby replacing thedisinfecting water with the pre-treated make-up water. The deaerator 9,the reductive water preparing device 3, the oxidation-reductionpotentiometer 5, and the dissolved hydrogen concentration meter 6 arethen turned on. The water circulating within the system is converted toreductive water having the dissolved oxygen concentration of 3 mg/l orlower, the dissolved hydrogen concentration of 0.1 mg/l or higher, andthe standard oxidation-reduction potential of −0.3V or lower asdetermined on the basis of the hydrogen electrode standard. Thereductive water is controlled to maintain these conditions.

[0036] The object of heat exchange 71 is cooled in the cooling device 7.In turn, the reductive water that received heat from the object of heatexchange 71 in the cooling device 7 is cooled by passing through thereductive water cooler 2. The reductive water cooler 2 cools thereductive water using a coolant 21 such as water or air.

[0037] When the quality of the reductive water has deteriorated after along-term circulation, the circulating reductive water is partially orcompletely discharged via the discharge piping 82 to the outside of thesystem. The discharged amount is compensated by introducing the make-upwater treated in the pre-treatment device 61 from the outside of thesystem via the supply piping 81.

[0038] According to the present invention, reductive water is employedas the heat exchange water for circulation in the heat exchangeapparatus. The circulation system is thereby maintained under areductive condition. Accordingly, oxidation and corrosion of metalmaterials of liquid ends can be reliably prevented. As it is difficultfor aerobic microorganisms and algae which form biological films to growunder reductive conditions, formation of such films can be effectivelysuppressed. The system only requires installation of simple devices, anddoes not otherwise incur any expense machinery costs.

[0039] The reductive water is a hydrogen-dissolved water obtained bydissolving hydrogen gas, and has the standard oxidation-reductionpotential of −0.3V or lower as determined on the basis of the hydrogenelectrode standard, the dissolved oxygen concentration of 3 mg/l orlower, and the dissolved hydrogen concentration of 0.1 mg/l or higher.Use of such reductive water reliably prevents oxidation and corrosion ofmetal materials of liquid ends. Moreover, such reductive water having adesired level of standard oxidation-reduction potential can easily beobtained. The present system uses no chemicals that conventionallyrequired purchasing costs, and storage space, and caused concerns aboutinfluences on the environment. This easily-obtained reductive water alsoserves to inhibit corrosion of materials used in the system andformation of biological films, while reducing adverse effects on theenvironment.

[0040] The reductive water is prepared by dissolving a reducing agent indeaerated water, and has a dissolved oxygen concentration of 3 mg/l orlower. It is therefore possible to prepare the reductive water using areduced dissolved amount of reducing agent.

[0041] When the coolant 21 in the reductive water cooler 2 is water, itis also preferable to use the above-described reductive water as thecoolant 21. This can prevent corrosion due to oxidation of metalmaterials and growth of microorganisms in the flow path of the coolant21 in the reductive water cooler 2. It is further preferable tocirculate the coolant 21 in a circulation system similar to that of thereductive water.

[0042] Referring to FIG. 2, a heat exchange system according to a secondembodiment of the present invention will next be explained. FIG. 2 is adiagram showing an example of the embodiment. Components in FIG. 2 thatcorrespond to those in FIG. 1 are labeled with corresponding numerals.Explanation for these common components will not be repeated, and onlythe differing points are described below. The difference between thepresent embodiment and FIG. 1 is that a substantially sealed bypasspiping 41 that branches from the circulation piping 4 is provided.Specifically, the bypass piping 41 is connected so as to branch from andreturn to the circulation piping 42 between the reductive water cooler 2and the oxidation-reduction potentiometer 5. Furthermore, the deaerator9 and the reductive water preparing device 3 are disposed on this bypasspiping 41. Valves V1, V2 are provided in the circulation piping 42 andthe bypass piping 41, respectively, in positions immediately downstreamof the branching. These valves are used to control through which path tocirculate the heat exchange water.

[0043] For example, by starting up the deaerator 9 and the reductivewater preparing device 3 when valve V1 is closed and valve V2 is openedto circulate the heat exchange water via the bypass piping 41, reductivewater can be supplied for circulation as the cooling water for thecooling device 7. The valves V1, V2 may be periodically opened andclosed, or may alternatively be controlled according to the measuredvalues of the oxidation-reduction potentiometer 5 or the dissolvedhydrogen concentration meter 6. It is also possible to allow a portionof the circulating water to constantly branch off and flow through thebypass piping 41. The heat exchange system 10 b according to the secondembodiment offer advantages similar to those of the first embodiment.Further, as the present embodiment enables installation of a small-scalereductive water preparing device in a location branched off from thecirculation system, existing heat exchange systems can be retrofittedwith ease.

[0044] Referring to FIG. 3, a heat exchange system according to a thirdembodiment of the present invention will next be explained. FIG. 3 is adiagram showing an example of the embodiment. Components in FIG. 3 thatcorrespond to those in FIG. 1 are labeled with corresponding numerals.Explanation for those common components will not be repeated, and onlythe differing points are described below. In the present embodiment, thedeaerator 9 and the reductive water preparing device 3 are not locatedwithin the circulation piping 4, but installed on external piping 43connected to the circulation piping 4. The pre-treatment device 61 fortreating the make-up water is provided before the deaerator 9, and thesupply piping 81 connects the pre-treatment device 61 and the deaerator9. According to this arrangement, reductive water is added to thecirculating water in use via the external piping. The standardoxidation-reduction potential and the dissolved hydrogen concentrationof the circulating heat exchange water (the circulating water) areconstantly monitored using the oxidation-reduction potentiometer 5 andthe dissolved hydrogen concentration meter 6 to accordingly control thedissolution amount of hydrogen gas. In this way, the standardoxidation-reduction potential of the circulating water is controlled toa desired level in a stable manner.

[0045] Referring to FIG. 5, a heat exchange system according to a fourthembodiment of the present invention will next be explained. FIG. 5 is adiagram showing an example of the embodiment. components in FIG. 5 thatcorrespond to those in FIG. 1 are labeled with corresponding numerals.Explanation for these common components will not be repeated, and mainlythe differing points are described.

[0046] Within the heat exchange system 10 d of the present embodiment, acirculation system referred to as a second system A is configured in thesame way as the heat exchange system 10 a of FIG. 1 except that thecooling device 7 is removed from the circulation piping 4. Providedseparately is a first system B comprising the cooling device 7, a pump64 (first reductive water supply device) for supplying reductive waterto the cooling device 7, and circulation piping 67 (first reductivewater circulation piping) connected so as to form a circulation systemwith the cooling device 7 and the pump 64. Connected at positionsdownstream of the dissolved hydrogen meter 6 of the second system A area reductive water supply side piping 70 for supplying reductive water tothe first system B, and a reductive water exit side piping 66 forreceiving reductive water from the first system B.

[0047] A flow rate adjustment valve 63 is provided on the reductivewater supply side piping 70. The flow rate of the reductive waterflowing into the first system B is controlled using this flow rateadjustment valve 63. The amount of reductive water supplied to the firstsystem B is adjusted by operating this flow rate adjustment valve 63 andthe valves (not shown) located at the cooling water inlet 62 and thecooling water outlet 68, resulting in adjustment of the amount ofreductive water (heat exchange water) flowing into the cooling device 7.This reductive water is water cooled in the reductive water cooler 2. Byadjusting the flow rate of the reductive water in the cooling device 7,the temperature of the reductive water can be controlled to a desiredlevel.

[0048] The second system A is identical to the system of FIG. 1 exceptin that the cooling device 7 is removed from the circulation piping 4.The second system A comprises the circulation pump 1 for supplyingreductive water to the first system B, the reductive water cooler 2 forcooling the reductive water exiting from the cooling device 7, thereductive water preparing device 3, and the circulation piping 4connected so as to form a circulation system with the circulation pump1, the reductive water cooler 2, and the reductive water preparingdevice 3. In this heat exchange system 10 d, the temperature of thereductive water circulating in the second system A is lower than thetemperature of the reductive water circulating in the first system B.The numeral 74 denotes a check valve.

[0049] In FIG. 5, the reductive water cooled to approximately 10° C. inthe reductive water cooler 2 of the second system A is first supplied tothe cooling device 7 of the first system B via the circulation piping 4,the cooling water inlet 62, the reductive water supply side piping 70,and the pump 64. The cooling device 7 cools, for example, heat loadcomponents requiring cooling which constitute a microwave oscillator ora dry pump. The temperature of the reductive water flowing in thecooling device 7 is constantly monitored by a temperature sensor 65. Aportion of the reductive water exiting the cooling device 7 passesthrough the circulation piping 67, and another portion of the reductivewater passes through the reductive water exit side piping 66 and entersthe circulation piping 4 of the second system A via the cooling wateroutlet 68. When the temperature monitored by the temperature sensor 65reaches a predetermined maximum allowable temperature or higher, thetemperature signal is converted into an electric signal for transmissionthrough circuits such as a control circuit and drive circuit. Thissignal is used to widened the opening of the flow rate adjustment valve63. By widening the opening of the valve, the amount of reductive waterflowing into the circulation line (the first system B) increases,thereby lowering the temperature of the reductive water flowing in thecooling device 7. When the temperature of the object of cooling becomeslower than the predetermined maximum allowable temperature, the openingof the flow rate adjustment valve is reduced to restrict the flow of thereductive water. In this way, the amount of reductive water circulatedfor cooling the object of cooling 71 can be constantly controlled to anoptimal level. In some cases where the facility is not in constantoperation, there is time when no heat load is generated. According tothe present embodiment, the flow of reductive water can be almoststopped during such shutdown times, preventing wasteful use of reductivewater. It is also preferable to provide a valve 91 in the circulationpiping 4 at a position between the cooling water inlet 62 and thecooling water outlet 68. By providing such a valve 91, the amount ofcirculated water in the second circulation system A can be adjusted asdesired.

[0050] When simultaneously cooling a plurality of objects of cooling 71,it is preferable to provide a corresponding system B for each object 71,and connect the plurality of systems B to the system A. According tothis arrangement, reductive water can be circulated through only any oneor more systems B which require reductive water.

[0051] Referring to FIG. 6, a heat exchange system according to a fifthembodiment of the present invention will next be explained. FIG. 6 is adiagram showing an example of the embodiment. Components in FIG. 6 thatcorrespond to those in FIG. 5 are labeled with corresponding numerals.Explanation for those components will not be repeated, and mainly thediffering points are described.

[0052] The heat exchange system 10 c of the present embodiment isconfigured in the same way as the heat exchange system 10 d of FIG. 5except that the cooling device 7 in the first system B is now providedin a plural number (four). The cooling devices 7 are connected in seriesand in parallel. Further, the temperature sensor 65 is positioned on thepiping just before the plurality of cooling devices 7, so as to monitorthe temperature of reductive water flowing through that piping. Usingsuch an arrangement and operating the valves (not shown) located at thecooling water inlet 62 and the cooling water outlet 68, reductive waterat a predetermined temperature can be circulated efficiently in theplurality of cooling devices 7.

[0053] As the heat load is greatly increased in this embodiment, theflow adjustment valve 63 should be a type that can vary the flow rate toa high flow rate. According to the heat exchange system 10 e of thepresent embodiment, a cooling system using an optimal amount of coolingwater and having enhanced temperature uniformity can be achieved.

[0054] Referring to FIG. 7, a heat exchange system according to a sixthembodiment of the present invention will next be explained. FIG. 7 is adiagram showing an example of the embodiment. Components in FIG. 7 thatcorrespond to those in FIG. 5 are labeled with corresponding numerals.Explanation for those components will not be repeated, and mainly thediffering points are described. The heat exchange system 10 f of thepresent embodiment differs from that of FIG. 5 in that a buffer tank(cooling water tank) 69 is now disposed on the circulation piping 67 ofthe first system B in the heat exchange system 10 d of FIG. 5. Thebuffer tank is connected so as to constitute a part of the sealedsystem, and is provided for storing cooled reductive water. Further, acheck valve 50 is disposed on the cooling water exit side piping 66.This arrangement is suitable when the object of cooling must be promptlycooled by the heat exchange system 10 f. Specifically, during a shutdowntime when the facility is not in operation, the flow adjustment valve 63is almost completely closed, while a large amount of reductive water isaccumulated in advance in the buffer tank 69. When the facility isrestarted, the pump 64 is operated to promptly circulate the reductivewater stored in the buffer tank 69. The cooled reductive water passesthrough the cooling device 7, and a portion of the water subsequentlyflows out via the check valve 50, the cooling water exit side piping 66,and the reductive water outlet 68, into the circulation piping 4 of thesecond system A. The remaining portion of the water flows through thecirculation piping 67. The temperature sensor 65 monitors thetemperature of the reductive water flowing in the cooling device 7. Asthe facility continues its operation, the temperature of the reductivewater increases. When the temperature exceeds a predetermined maximumallowable level, a temperature signal is supplied as a feedback to openthe flow rate adjustment valve 63, thereby introducing new reductivewater. As a large amount of reductive water is accumulated in advance,this system can deal with cases requiring prompt cooling, such as arapid heat treatment furnace used in a semiconductor manufacturingprocess. When the operation of the facility is stopped, the pump 64 isoperated while the flow rate adjustment valve 63 is fully opened, so asto accumulate cooled reductive water in the buffer tank 69 inpreparation for the next facility operation. When accumulating cooledreductive water in the buffer tank 69, the check valve 50 functions toprevent reductive water on the high-temperature side from flowing intothe buffer tank, so as to maintain the water temperature in the buffertank 69 at the temperature of the cooled water entering the tank.

[0055] In the fourth, fifth, and sixth embodiments, the second system Ais not limited to the above-described example. The second system A maybe a circulation system configured as the heat exchange system 10 b ofFIG. 2 without the cooling device 7, or as the heat exchange system 10 cof FIG. 3 without the cooling device 7. It is also preferable to providea plurality of first systems B.

[0056] Referring to FIG. 8, a heat exchange system according to aseventh embodiment of the present invention will next be explained. FIG.8 is a diagram showing an example of the embodiment. Components in FIG.8 that correspond to those in FIG. 5 are labeled with correspondingnumerals. Explanation for those components will not be repeated, andmainly the differing points are described. The apparatus 10 g forcooling an object of heat exchange according to the present embodimentdiffers from FIG. 5 in that the second system A of the heat exchangesystem 10 d in FIG. 5 may be of any type (of cooling water supplysystem) as long as it can supply cooling water (heat exchange water) tothe first system B. Specifically, the cooling water supply system of thepresent embodiment may either be a substantially sealed system or anunsealed system. The cooling water in this embodiment may be, withoutlimitation, tap water, river water, industrial water, filtered waterobtained by eliminating particle components and oxidizers such ashypochlorous acid and sodium hypochlorite from those waters, deionizedwater obtained by treating those waters in a water purifying apparatusto eliminate ionic and non-ionic substances, or the above-mentionedreductive water. The reductive water may be prepared as described above.

[0057] In FIG. 8, the temperature sensor 65 constantly monitors thetemperature of the cooling water flowing in the cooling device 7. Thecooling water cooled to about 10° C. in the cooling water cooler (notshown) within the cooling water supply system passes through the coolingwater supply piping 4 a, and is introduced into the cooling device 7 viathe cooling water inlet 62, the flow rate adjustment valve 63, and thepump 64. A portion of the cooling water exiting the cooling device 7flows through the cooling water circulation piping 67, while theremainder exits from the cooling water outlet 68 to enter the coolingwater exit piping 66 a. When the temperature monitored by thetemperature sensor 65 reaches the predetermined maximum allowabletemperature or higher, the temperature signal is converted into anelectric signal for transmission through circuits such as a controlcircuit and drive circuit. This signal is used to further widen theopening of the flow rate adjustment valve 63. By further widening theopening of the valve, the amount of cooling water flowing into thecirculation line increases, thereby lowering the temperature of thecooling water flowing through the cooling device 7. When the temperatureof the object of heat exchange becomes lower than the predeterminedminimum allowable temperature, the opening of the flow rate adjustmentvalve 63 is reduced to restrict the cooling water amount. In this way,the amount of cooling water for cooling the heat exchanger 7 can beconstantly controlled to the minimum required level. In some cases wherethe facility is not in constant operation, there is time when no heatload is generated. According to the present embodiment, the flow ofcooling water can be almost stopped during such shutdown time,preventing wasteful consumption of cooling water. The numeral 73 in FIG.8 denotes a heat insulating material. By providing the heat insulatingmaterial 73 as shown, it is possible to avert influences by the ambienttemperature, allowing more efficient operation. Condensation can also beprevented.

[0058] Referring to FIG. 9, a heat exchange system according to aneighth embodiment of the present invention will next be explained. FIG.9 is a diagram showing an example of the embodiment. Components in FIG.9 that correspond to those in FIG. 6 are labeled with correspondingnumerals. Explanation for those components will not be repeated, andmainly the differing points are described. The apparatus 10 h forcooling an object of heat exchange according to the present embodimentdiffers from FIG. 6 in that the second system A of the heat exchangesystem 10 e in FIG. 6 may be of any type (of cooling water supplysystem) as long as it can supply cooling water to the first system B.Specifically, the cooling water supply system of the present embodimentmay be either a substantially sealed system or an unsealed system. Thetypes of cooling water that can be used are the same as those listed forthe above-described seventh embodiment. By implementing the apparatus 10h for cooling an object of heat exchange according to the presentembodiment, a cooling system using minimum cooling water and havingenhanced temperature uniformity can be realized.

[0059] Referring to FIG. 10, a heat exchange system according to a ninthembodiment of the present invention will next be explained. FIG. 10 is adiagram showing an example of the embodiment. Components in FIG. 10 thatcorrespond to those in FIG. 7 are labeled with corresponding numerals.Explanation for those components will not be repeated, and mainly thediffering points are described. The apparatus 10 i for cooling an objectof heat exchange according to the present embodiment differs from FIG. 7in that the second system A of the heat exchange system 10 f in FIG. 7may be of any type (of cooling water supply system) as long as it cansupply cooling water to the first system B. Specifically, the coolingwater supply system of the present embodiment may be either asubstantially sealed system or an unsealed system. The types of coolingwater that can be used are the same as those listed for theabove-described seventh embodiment. The apparatus 10 h for cooling anobject of heat exchange according to the present embodiment offersadvantages similar to those of the sixth embodiment.

[0060] The circulation pump used as the reductive water supply deviceand the cooling water supply device can be of any known type that arenormally used. However, it is preferable to use a circulation pumphaving a structure such that the heat exchange water or the coolingwater does not come in contact with air at the sealing portion betweenthe motor and the impeller of the circulation pump. The sealingstructure at this sealing portion may be formed by introducing an inertgas into the sealing portion.

EXAMPLES

[0061] The present invention is described below in further detail usingspecific examples. These examples are provided only for illustrativepurposes and by no way limit the present invention.

Example 1

[0062] A heat exchange system having a flow configuration as shown inFIG. 2 (the circulation system is a sealed system) was employed toperform tests according to the installation specifications and operatingconditions listed below and the quality of circulating water indicatedin Table 1. The results after 30 days of continuous operation are shownin Table 1. The quality of circulating water was determined by analyzingthe water sampled at point C in FIG. 2.

[0063] The object of heat exchange: a heat radiating portion of asemiconductor manufacturing apparatus

[0064] Piping material: stainless steel bright annealed tube; ⅜ inchesdiameter

[0065] Total piping length: 150 m

[0066] Deaeration method: vacuum deaeration using gas-permeable membrane

[0067] Hydrogen dissolution method: membrane dissolution usinggas-permeable membrane

[0068] Circulation flow rate: 10/min. The entire circulating water wasconstantly circulated through the deaerator 9 and the hydrogen gasdissolution tank 32, with no make-up or discharge of circulating water.

[0069] Temperature of reductive water before cooling by the coolingdevice: 10° C.

[0070] Temperature of reductive water after cooling by the coolingdevice: 23° C.

[0071] Metal concentration in raw water: 0.25 μg Fe/L

[0072] Number of live bacteria in raw water: 2/L

[0073] Circulated time: 30 days

[0074] Evaluation: examination of the condition of the piping internalsurface and water quality analysis of the reductive water after 30 daysTABLE 1 Quality of circulating water or Compara- condition of tivepiping internal Raw Specific examples examples surface water 1 2 3 4 5 12 Deaeration No No Yes Yes Yes Yes No Yes treatment Dissolved oxygen 8.28.0 5.0 3.0 3.0 0.05 8.4 0.05 concentration (mg O/L) Dissolution of NoYes Yes Yes Yes Yes No No hydrogen Dissolved 0 1.1 1.1 0.3 1.1 1.1 0 0hydrogen concentration (mg H/L) Standard +600 0 −100 0 −400 −400 +600+480 oxidation- reduction potential (mV vs. NHE) Metal — 3.6 3.2 3.50.26 0.26 213 119 concentration (μg Fe/L) Number of live — 20 11 18 2 24256 835 bacteria per mL Condition of the — Δ Δ Δ ◯ ◯ × × pipinginternal surface

Example 2

[0075] Using the apparatus 10 g for cooling an object of heat exchangehaving the flow configuration shown in FIG. 8, measurements were maderegarding the used (consumed) amount of cooling water during apredetermined period of time. The average temperature on the coolingwater supply side (T1) and the average temperature on the exit side (T2)of the cooling device 7 were also measured. For comparison, aconventional heat exchange system configured similarly to the heatexchange system 10 g but without the temperature sensor 65 was operatedunder the same conditions. In this system for comparison, measurementswere similarly made regarding the used (consumed) amount of coolingwater within the same predetermined period of time, the averagetemperature on the cooling water supply side (T3), and the averagetemperature on the exit side (T4) of the cooling device 7. The resultsshowed that, using the amount of reductive water consumed by theconventional cooling apparatus as the base amount with a value of 100,the proportional value of the amount of reductive water used by thecooling apparatus 10 g having the flow configuration shown in FIG. 8 was36. This indicates that the used amount of cooling water was reduced bymore than 60%. Further, whereas (T4−T3) was approximately 8° C., (T2−T1)was approximately 0.2° C., producing only a very slight temperaturedifference. From this fact, it was found that the cooling apparatus 10 ghaving the flow configuration shown in FIG. 8 can minimize thedifference between temperatures on the supply side and the exit side ofthe cooling device, and is therefore favorable when requiring highlyprecise temperature control.

What is claimed is:
 1. A heat exchange water for cooling an object ofheat exchange such as machinery, air, or liquid, wherein said heatexchange water is reductive water having zero or negative standardoxidation-reduction potential as determined on the basis of the hydrogenelectrode standard.
 2. The heat exchange water defined in claim 1,wherein said reductive water is hydrogen-containing water obtained bydissolving hydrogen gas in water, has a standard oxidation-reductionpotential of −0.3 V or lower as determined on the basis of the hydrogenelectrode standard, and has a dissolved hydrogen concentration of 0.1mg/L or higher.
 3. The heat exchange water defined in claim 2, whereinsaid reductive water has a dissolved oxygen concentration of 3 mg/L orlower.
 4. The heat exchange water defined in claim 1, wherein saidreductive water is obtained by dissolving a reducing agent in deaeratedwater, has a standard oxidation-reduction potential of −0.3 V or loweras determined on the basis of the hydrogen electrode standard, and has adissolved oxygen concentration of 3 mg/L or lower.
 5. The heat exchangewater defined in claim 1, wherein said reductive water is used ascooling water in a heat exchanger for cooling an object of heat exchangein an apparatus for manufacturing electronic components.
 6. A heatexchange system for performing heat exchange by supplying heat exchangewater to a heat exchanger, comprising: a heat exchanger for performingheat exchange between an object of heat exchange such as machinery, air,or liquid, and reductive water having zero or negative standardoxidation-reduction potential as determined on the basis of hydrogenelectrode; a reductive water supply device for supplying said reductivewater to said heat exchanger; a reductive water cooler for cooling saidreductive water; and a reductive water circulation piping connected soas to form a circulation system with said heat exchanger, said reductivewater supply device, and said reductive water cooler; wherein saidcirculation system of reductive water is substantially a sealed system.7. The system defined in claim 6, further comprising: bypass pipingbranching from an end or mid portion of said reductive water circulationpiping and re-connecting to said reductive water circulation piping;wherein a reductive water preparing device for preparing said reductivewater is connected at a position on said bypass piping, and saidcirculation system of reductive water including said reductive waterpreparing device and said bypass piping forms a substantially sealedsystem.
 8. The system defined in claim 6, further comprising: externalpiping connected to said reductive water circulation piping; and areductive water preparing device for preparing said reductive waterconnected in a position on said external piping; wherein saidcirculation system of reductive water including said external piping andsaid reductive water preparing device is substantially a sealed system.9. A heat exchange system for performing heat exchange by supplying heatexchange water to a heat exchanger, comprising: a heat exchanger forperforming heat exchange between an object of heat exchange such asmachinery, air, and liquid, and a cooling water; a cooling water supplydevice for supplying said cooling water to said heat exchanger; coolingwater circulation piping connected so as to form a circulation systemwith said heat exchanger and said cooling water supply device; a coolingwater inlet for introducing said cooling water from outside into saidcooling water circulation piping; a cooling water outlet for dischargingsaid cooling water from said cooling water circulation piping tooutside; a flow rate adjustment valve for adjusting flow rate of saidcooling water supplied from said cooling water inlet into said coolingwater circulation piping; a cooling water supply system configured so asto supply cooling water having a temperature lower than said coolingwater circulating within said cooling water circulation piping from saidcooling water inlet into said cooling water circulation piping, and,after said cooling water is discharged from said cooling water outletand cooled in a cooler, to again supply said cooling water from saidcooling water inlet; and a controller for controlling said flow rate ofsaid cooling water passing through said flow rate adjustment valve tothereby control temperature of said cooling water flowing in saidcooling water circulation piping to a desired temperature.
 10. Thesystem defined in claim 9, further comprising: a cooling water tank foraccumulating a predetermined amount of said cooling water within saidcooling water circulation piping.
 11. The system defined in claim 9,wherein said cooling water is reductive water having zero or negativestandard oxidation-reduction potential as determined on the basis of thehydrogen electrode standard, and said circulation system of coolingwater is substantially a sealed system.
 12. The system defined in claim9, wherein a reductive water preparing device for preparing reductivewater is connected within said cooling water supply system in series orin parallel, or connected outside of said cooling water supply system,and said circulation system of cooling water including said reductivewater preparing device forms a substantially sealed system.
 13. Thesystem defined in claim 9, further comprising: a check valve forpreventing said cooling water from flowing in reverse from said coolingwater outlet into said cooling water circulation piping.
 14. The systemdefined in claim 6, wherein said reductive water circulation piping orsaid cooling water circulation piping is surrounded by a heat insulatingmaterial.
 15. The system defined in claim 6, further comprising:discharge piping for partially or completely discharging watercirculating in said circulation system to the outside of saidcirculation system, and/or a supply piping for supplying make-up waterfor adjusting said circulating water
 16. The system defined in claim 6,further comprising: a standard oxidation-reduction potential measuringdevice for measuring standard oxidation-reduction potential of saidreductive water prepared in said reductive water preparing device;wherein said reductive water preparing device is controlled according tomeasurement results of said standard oxidation-reduction potentialmeasuring device.
 17. The system defined in claim 6, further comprising:a dissolved hydrogen concentration measuring device for measuringdissolved hydrogen concentration of said reductive water prepared insaid reductive water preparing device; wherein said reductive waterpreparing device is controlled according to measurement results of saiddissolved hydrogen concentration measuring device.
 18. The systemdefined in claim 6, wherein a medium that performs heat exchange in saidreductive water cooler with the circulating water is reductive waterhaving zero or negative standard oxidation-reduction potential.